Pressure-operated electrical switch responsive to a pressure decrease after a pressure increase

ABSTRACT

A pressure-operated electrical switch with means to hold the switch closed until the pressure increases to a first predetermined value and then decreases to a second predetermined value at which time the holding means is released and the switch is opened. The holding means consists of a rod pivoted at one end with a tension spring attached near the other end of the rod. The releasing means includes a pawl attached to the other end of the rod, a compression spring subjected to the pressure, a second rod with one of its ends attached to said compression spring and with a hook on its other end to slip over said pawl and pull the pivoted rod away from the switch.

United States Patent [72] Inventor Frederick W. Gibson Hampton, Va. 21 Appl. No. 881,041 [22] Filed Dec. 1, 1969 [45] Patented Sept. 28, l9 7 1 V v V [73] Assignee The United States of America as T" represented by the Administrator of the National Aeronautics and Space Administration [54] PRESSURE-OPERATED ELECTRICAL SWITCH RESPONSIVE TO A PRESSURE DECREASE AFTER A PRESSURE INCREASE 3 Claims, 3 Drawing Figs.

[52] U.S.Cl 200/81 R, 200/82 C [51] Int. Cl ...H0lh43/28, 1-10 1 h 3 5/24 [50] Field of Search 200/81, 82, 82.2, 83.91; 335/123, 140

[56] References Cited UNITED STATES PATENTS 2,492,261 12 1949 Bordelon 200/82 .2

Primary ExaminerRobert K. Schaefer Assistant Examiner-Robert A. Vanderhye Attorneys--l-loward J. Osborn, William H. King and G. T.

McCoy ABSTRACT: A pressure-operated electrical switch with means to hold the switch closed until the pressure increases to a first predetermined value and then decreases to a second predetermined value at which time the holding means is released and the switch is opened. The holding means consists of a rod pivoted at one end with a tension spring attached near the other end of the rod. The releasing means includes a pawl attached to the other end of the rod, a compression spring sub jected to the pressure, a second rod with one of its ends attached to said compression spring and with a hook on its other end to slip over said pawl and pull the pivoted rod away from the switch.

SWITCH ENERGY SOURCE PATENTED SE28 IBYI 346090271 FIG. 1

ENERGY SOURCE ZLV/ 3/0/01/11/1/ SWITCH 2o swncu ll 25 it 2 ENERGY SOURCE c? PNEUMATIC L w CYLINDER ,3o

l b ENERGY SOURCE FIG. 3 INVENTOR.

FREDERICK W. GIBSON BY 2.4 s

ATTOR YS PRESSURE-OPERATED ELECTRICAL SWITCH RESPONSIVE TO A PRESSURE DECREASE AFTER A PRESSURE INCREASE ORIGIN OF THE INVENTION The invention described herein was made by an employee of the United States Government and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The invention relates generally to an electrical switch and more specifically concerns a pressure-operated switch that operates if the pressure changes in one direction to or beyond a first predetermined value and then changes in the other direction to a second predetermined value.

In many processes certain sequential events occur without regard to time. The triggering of each event is dependent on the magnitude of some variable involved in the process such as pressure. The triggering of an event in a process of this type is usually done by a pressure-operated switch. That is, when the pressure exerted on the switch reaches some predetermined value the switch is actuated thereby causing the electrical circuit in which the switch is located to perform some step in the process. As long as the trigger of an event depends only on the magnitude of the pressure there is not problem. However, consider the following problem: pressure-actuated electrical switches are used to control a double-acting valve pneumatic cylinder combination which positions a protective cone in front of a model in a hypersonic wind tunnel. After the tunnel has started, at some preselected stagnation pressure, the cylinder retracts and pulls the protective cone out of the flow. The tunnel stagnation pressure then increases to the desired maximum value and then begins to decrease. When the pressure has dropped to a certain desired value, the pneumatic cylinder returns the cone to its position in front of the model to protect the model during the tunnel shutdown. To solve this problem, it is necessary to use switches to apply a voltage to the cylinder at the time the stagnation pressure is reached and disconnect the voltage when the pressure drops to said certain desired value. It is not problem to use a pressure-actuated switch to close an electrical circuit and apply a voltage to the cylinder at the time the stagnation pressure is reached. The problem is to use a pressure-actuated switch to open the electrical circuit and disconnect the voltage from the cylinder when the pressure drops to the certain desired value after it has reached the desired maximum value. It is therefore the primary purpose of this invention to provide a pressure-actuated switch that is actuated only after the pressure has reached a certain desired value and then drops to a predetermined lower value.

SUMMARY OF THE INVENTION The invention consists of a switch held in its actuated position with a beam pivoted at one of its ends and a tension spring attached to the beam near its other end. A pawl is attached to the other end of the beam. A compression spring is subjected to the pressure that operates the switch. One end of a rod is attached to the compression spring with the other end of the rod having a hook on it such that when the pressure exceeds a predetermined value the hook slips over the pawl. Then as the pressure decreases the hook pulls the pawl. When the pressure falls below a predetermined value the beam is pulled away from the switch allowing it to assume its normal position. In another embodiment of the invention the embodiment of the invention described above is connected in series electrically with a second pressure operated switch.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of the mechanical features of one embodiment of the invention;

FIG. 2 is a schematic drawing of the embodiment of the invention in FIG. 1 in combination with another switch to form another embodiment of the invention; and

FIG. 3 is a schematic drawing of the switches in FIG. 2 connected in an electrical circuit to control a particular process.

DETAILED DESCRIPTION OF THE INVENTION Turning now to the embodiment of the invention selected for illustration in FIG. 1 of the drawings the number 11 designates a switch that is attached to a fixed structure 12. Switch 11 is actuated by means ofa button 13. That is, when button 13 is out in its normal position switch I] is open and when button 13 is pushed in switch 11 is closed. A rod 14 is pivotally attached at one of its ends to a fixed structure 15 by a pivot 16. A pawl 17 is pivotally attached to the other end of rod 14 by a pivot 18 so that the pawl will rotate only in a clockwise direction from the position shown. A tension spring 19 is attached to rod 14 and pawl 17 to hold pawl 17 in the position shown. A tension spring 20 is attached to fixed structure l2 and rod 14 to pull rod 14 against button 13 to hold switch 11 closed. A compression spring 21 is located in the energy source whose pressure controls switch 11. A rod 22 having a hook 23 at one of its ends has its other end attached to the compression spring 21.

In the operation of the embodiment of the invention shown in FIG. 1, as the pressure of the energy source increases, spring 21 compresses pushing hook 23 against pawl 17. The pressure exerted against pawl 17 by hook 23 rotates pawl 17 in a clockwise direction about pivot 18. When the pressure of the energy source reaches some predetermined value, determined by tension spring 19, hook 23 slips over pawl 17. Thereafter as the pressure of the energy source decreases, hook 23 pulls against pawl 17 which tends to rotate rod 14 in a counterclockwise direction about pivot 16. When the pressure of energy source decreases to a predetermined value, determined by tension spring 20, rod 14 is pulled enough away from button 13 allowing switch 11 to open. Hence switch 11 is initially closed and remains closed until the pressure of the energy source increases to a first predetermined value and then decreases to a second predetermined value.

Referring now to FIG. 2 there is shown a second switch used in combination with the embodiment of the invention disclosed in FIG. 1. A switch 25 having an actuating button 26 is attached to a fixed structure 27. Switch 25 is normally open and when button 26 is pushed the switch is closed. A compression spring 28, located within the energy source, has one end of a rod 29 attached to it such that when the spring is com pressed the other end of the rod pushes button 26 and closes switch 25. FIG. 3 shows how switches 11 and 25 are connected electrically to solve the problem proposed above. When both of these switches are closed a voltage E is applied to a pneumatic cylinder 30 and cone 31 is pulled out from the front of the model 32. When either or both of the switches are open the voltage E is not applied to cylinder 30 and cone 31 is in front of model 32 as shown.

In the operation of the apparatus disclosed in FIGS. 2 and 3, switch 25 is initially open and switch 11 is initially closed. Since these two switches are in series the voltage E is not applied to pneumatic cylinder 30. Hence cone 31 is in front of model 32. After starting the energy source and its pressure increases to some preselected value, switch 25 is closed thus completing the circuit. Pneumatic cylinder 30 is activated and protective cone 31 is retraced out of the flow of the energy source. After the pressure of the energy source increases to a maximum value then decreases to a second preselected value switch 11 opens and pneumatic cylinder 30 again places cone 31 in front of model 32.

The advantages of this invention are that it may be used to arrange the order of occurrence of events, without regard to time, in many processes in which one or more of the variables has a rate-of-change which reverses in sense at some time in the process.

What is claimed to be new and desired to be secured by Letters Patent of the United States is:

l. A pressure-operated switch comprising: a switch including a button for actuating the switch; means for holding said button so that said switch is in its actuated position; said holding means includes a rod pivoted at one end and a tension spring attached to the rod near its other end and to a fixed structure to hold said rod against said button to depress it; and means for releasing said holding means when said pressure increases to a first predetermined value and then decreases to a second predetermined value whereby the switch assumes its unactuated position.

2. A pressure-operated switch according to claim 1 wherein said releasing means includes a pawl attached to said other end of said rod; a compression spring subjected to said pressure; and a second rod with one of its ends attached to said compression spring and with a hook on its other end said hook being located relative to said pawl so that when said pressure increases to said first predetermined value said hook slips over said pawl whereby when said pressure decreases to said second predetermined value said hook pulls said pivoted rod away from said button.

3. A switching arrangement comprising: a first pressureoperated switch and a second pressure-operated switch connected in series electrically and subjected to the same pressure system; means for closing said first switch when the pressure of said pressure system reaches a first predetermined value; means for holding said second switch in its closed position; and means for releasing said holding means when the pressure in said pressure system increases to a second predetermined value and then decreases to a third predetermined value greater than said first predetermined value whereby the circuit controlled by said first and second switches closes when the pressure in said pressure system reaches said first predetermined value and remains closed until the pressure rises to said second predetermined value and then decreases to said third predetermined value. 

1. A pressure-operated switch comprising: a switch including a button for actuating the switch; means for holding said button so that said switch is in its actuated position; said holding means includes a rod pivoted at one end and a tension spring attached to the rod near its other end and to a fixed structure to hold said rod against said button to depress it; and means for releasing said holding means when said pressure increases to a first predetermined value and then decreases to a second predetermined value whereby the switch assumes its unactuated position.
 2. A pressure-operated switch according to claim 1 wherein said releasing means includes a pawl attached to said other end of said rod; a compression spring subjected to said pressure; and a second rod with one of its ends attached to said compression spring and with a hook on its other end said hook being located relative to said pawl so that when said pressure increases to said first predetermined value said hook slips over said pawl whereby when said pressure decreases to said second predetermined value said hook pulls said pivoted rod away from said button.
 3. A switching arrangement comprising: a first pressure-operated switch and a second pressure-operated switch connected in series electrically and subjected to the same pressure system; means for closing said first switch when the pressure of said pressure system reaches a first predetermined value; means for holding said second switch in its closed position; and means for releasing said holding means when the pressure in said pressure system increases to a second predetermined value and then decreases to a third predetermined value greater than said first predetermined value whereby the circuit controlled by said first and second switches closes when the pressure in said pressure system reaches said first predetermined value and remains closed until the pressure rises to said second predetermined value and then decreases to said third predetermined value. 